An aneurysm is a localized, blood-filled balloon-like bulge of a blood vessel, caused by the weakening of the vessel wall. One type of aneurysm is an aortic aneurysm, which occurs in the main artery carrying blood from the left ventricle of the heart to the body. When the size of an aneurysm increases, there is a significant risk of rupture, resulting in severe hemorrhage, which may even lead to death. Aneurysms may be hereditary or caused by disease, either of which can lead to the weakening of the blood vessel wall.
For aneurysms in the aorta, arms, legs or head, the weakened section of the vessel may be replaced by a bypass graft that is sutured at the vascular stumps. Instead of sewing, the graft tube ends, which are made rigid and expandable by a nitinol wireframe, can be inserted into the vascular stumps and permanently fixed there by external ligature or an expandable ring. Less invasive endovascular techniques allow covered metallic stent grafts to be inserted through the arteries of the leg and deployed across the aneurysm.
Thus, when the aneurysm occurs in a region of a blood vessel where there is no branching leading to other blood vessels, stent grafts may be easily placed, thereby bypassing the aneurysm and highly reducing the risk of rupture. However, when the aneurysm occurs in the close vicinity of another blood vessel that branches off from the vessel with the aneurysm, it is sometimes impossible to place a stent graft without blocking the branch vessel. Such a condition occurs in approximately 40% of the patients diagnosed with an aortic aneurysm, wherein the length and diameter of the healthy vessel remaining between the aneurysm and the branch to the renal arteries, is insufficient to hold a stent graft in place. In such instances, stent grafts cannot be used, and certain patients are referred to invasive surgery. However, surgery is a relatively high risk procedure, and further, not all patients may be operated on, thus leaving a large number of patients with untreated, life threatening, aneurysms.
There are several published methods aiming at treating such aneurysms; however, they all suffer from various disadvantages.
One exemplary such method of treating such aneurysms is the preparation of a tailored stent graft, prepared according to the specific anatomy of the patient being treated. Such a tailored stent graft is prepared so that it includes openings at the branches, so as to allow blood to naturally flow from the main vessel into the side branch vessels. Such stent grafts are disclosed, e.g., in U.S. Patent Application Publication No. 2005/0171598. However, the preparation of such stent grafts is expensive and is time consuming, since each needs to be prepared specifically according to the anatomy of each treated patient. Further, the placement of such a tailored stent graft is relatively complicated, and therefore is a relatively long and high-risk procedure. Furthermore, such a procedure requires high expertise and is performed by only a very limited number of physicians.
Another method for treating such aneurysms is published in U.S. Patent Application Publication No. 2009/0240316 (“US '316”), although it is not known to be used in the art. According to the disclosure of US '316, a bloused stent-graft is deployed into a main vessel such that the bloused section of the bloused stent-graft covers the opening of a branch vessel emanating from the main vessel. The bloused section includes loose graft cloth, and a pressure differential between the main vessel and the branch vessel causes the bloused section to be forced into an ostium of the branch vessel, thereby creating a pocket aligned with the branch vessel. Further, according to US '316, a distal tip of a puncture device is located in the pocket and thus aligned with the branch vessel. An outward force is applied to the puncture device to cause the distal tip of the puncture device to puncture the bloused section, thus creating a collateral opening, or fenestration, in the bloused section precisely aligned with the branch vessel. However, it should be understood that the physician placing the stent graft monitors the placement thereof by following the blood flow. Therefore, once the bloused stent graft is placed, it would be impossible for the physician to see where the branching of the vessel is, since the blood flow has stopped. Therefore, it would be impossible, if not very difficult, to implement such a method as disclosed in US '316.
U.S. Patent Application Publication No. 2005/0131517 discloses a stent graft with a relatively flexible or variable fenestration, wherein the fenestration is placed at the branching vessel, and a branch vessel stent is placed in the branch vessel. However, it is questionable whether such a flexible fenestration would be able to fit the anatomy of any given patient.
As known in the art, similar difficulties are encountered when using stenting procedures for treating any endovascular conditions involving branching of the treated blood vessel. Such endovascular conditions include atherosclerotic vessel stenosis, iatrogenic stricture of a vessel, external pressure causing vessel lumen narrowing, aneurysmal dilatation, bleeding vessel, and any other condition that requires stenting of a bifurcated segment either by a dilating stent or a stent graft.
It would therefore be beneficial to develop a method by which a stent graft may be used effectively and efficiently, even in instances where the medical condition requiring stenting of a bifurcated segment occurs relatively close to a branching of the vessel.